The Australians behind Meghan Markle's engagement dress

When you think of the Australian designers who have been most successful in international circles, names including Collette Dinnigan, Kym Ellery and the Zimmermann sisters roll off the tongue.

But many in the fashion world would argue Australia's most successful export is Ralph & Russo, the brainchild of London-based expats Tamara Ralph and Michael Russo.

In 10 years, the pair have risen to the cr??me of the couture world, showing in Paris and dressing the likes of Angelina Jolie, Eva Longoria and Kylie Minogue.

Prince Harry and Meghan Markle in their official engagement portrait. Photo: Alexi Lubomirski

This week, they scored possibly their biggest coup yet, when Meghan Markle revealed she had chosen a Ralph & Russo creation for her official engagement portraits with Prince Harry.

The dress, with a sheer bodice, and flowing tulle skirt, is from the 2016 autumn/winter collection - it's a daring, if classy choice, choosing something that's not necessarily current season - and is said to cost nearly $100,000.

In explaining their decision to set up shop in London, Russo told Harper's Bazaar earlier this year: "It's a place to settle, as opposed to some of the other destinations for luxury. It's where our clients buy property and send their children to school. It feels like the centre of the universe."

For fittings, the pair's clients attend the couple's seven-storey townhouse in exclusive Mayfair, just a stone's throw, or a stroll through Green Park, from Buckingham Palace.

But their notoriety has spread beyond the UK; in 2013, In 2013, Fortune magazine listed the pair among the 40 most successful business people under 40, alongside Facebook founder Mark Zuckerberg.

While both opted for British-based designers, Catherine's Reiss dress was more conservative, although it did proceed to sell out in a matter of minutes.

At ??56,000 ($97,000), Markle's dress is less likely to move as many frocks but it will certainly turn Ralph & Russo into a household name. And with the pair's plans to open more than 10 boutiques and become more of a luxury design house than merely a couturier, the boost has come at just the right time.